Electric discharge lamp



Sept. 8, 1942. A, LQMPE ETAL 2,295,043

v ELECTRIC mscn nez: LAMP v Filed Ju ne27, 1940 lnven'tor's; Arved Lompe,

' Mar'ti Regen v Their Akbovneg.

Patented Sept. 8, 1942 UNIT-ED STAT ES PATENT I OFFICE ELECTRIC DISCHARGE LAMP Arved Lompe, Berlin, and Martin Reger, Berlin- Charlottenburg, Germany, assignors to General Electric Company, a corporation of New York Application June 27, 1940, Serial No. 342,780 In Germany June 28, 1939 3 Claims. ((1176-1552) The present invention relates to gaseous electric discharge lamps generally and more particularly the invention relates to suchv lamps of the positive column discharge type operating withlow gas pressure, that is, with a luminous,

diffuse positive column discharge.

Lamps of the above type provided with heated electrodes having a heater connected in series with the discharge to serve asseries ballast therefor are now known in the art, We haveobserved that in such known lamps satisfactory operation is obtained only when the ohmic resistance a discharge lampdevice comprises a tubular conlamp of the above type which is insensitive to fluctuations in line voltage. Still further objects and advantages'of the int ention will be apparent to those skilled in the art from the following detailed description thereof and from'the appended claims.

The invention attains its objects by separating the electrodes in thelamp containersuch distance that atleast sixty per cent or the voltage supplied to the apparatus is dissipated in the gaseous electric discharge between said electrodes and by connecting an iron-hydrogen resistor element in series with the electrode heaters and the discharge. The resistance of the iron-hydrogen element is not more than, and is preferably lower than, the total resistance of both the heater elements. I

In a lamp embodying the invention the discharge current is limited primarily by the heaters for the electrodes, the comparatively low resistance of the iron-hydrogen resistor serving mainly to preventexcessive fluctuations in current density and in luminous output of the discharge. Thus, it is possible to separate the electrodes'a greater distance thanhas been found practicable in prior lamps and to dissipate a greater proportion of the line voltage in the discharge resulting in a higher luminous efllciency. Any of the means well known in the art may be used for starting the discharge in the lamp. We prefer to connect the electrode heaters in series during the starting of the lamp by a lead external to the lamp containers. Preferably the lead contains a resistance and a switch, such as a thermostatic switch, for breaking the connection between the electrode heaters to start the discharge between the electrodes whensaid electrodes have been heated to adischarge supporting temperature. When desired, the current lead is cemented to the outer surface of the container or is, covered with an electrically insulating material and is mounted inside the container and along -the discharge path betweensaid electrodes. Thecurrtnt lead thus serves as an auxiliary electrode having a capacitive effect.

In the drawing accompanying and forming .part of this specification an embodiment of'th'e invention is-shown in a side elevational, partly sectional view. I

Referring to the drawing the gaseous electric tainer I. of vitreous material, such as glass or quartz. Said container is about 1 meter long,

has an internal diameter of about 25 mm. and

has a quantity 2 of mercury and a rare gas therein, such as argon, at a pressure of, about 2 mm. An electrode 3, 4 consisting of a nickel shell 3 coated with an activating material, such as barium oxide, and a tungsten wire 4 mounted inside said shell 3 is mounted adjacent the ends of said container I. Said electrodes 3. 4 are separated a distance such that when the operating current is about 100 milliamperes the voltage drop across the discharge path is ap-' proximately 155 volts. The heater wires 4 are connected in series with the discharge and an iron wire-hydrogen fllled resistor element 5 (of known structure) is connected in series with one of said heaters 4. The element 5 is mounted outside the container I and inside of the hollow stem thereof. During the operation of the lamp the voltage drop across each of the heaters 4 is about 20 volts and the voltage drop across the resistor element 5 is about 25 volts.

The electrodes3 are connected in series during the starting period by current lead 6 cemented to the outer surface of the container I. Said lead 6 is co-extensive with said container I and has a capacitive effect which ionizes the gaseous filling inthe container I to facilitate starting of the main discharge. A resistance I of about 1500 ohms is mounted in the hollow stem of the container I and is connected into said lead 6 in series with the electrode heaters 3. A bimetallic -an ultra-violet transmitting glass.

tainer I.

. this purpose.

[of between 100 and 300 milliamperes.

trodes 3, 4 when said electrodes 3, I have been heated to a discharge supporting temperature.

When desired the switch 8 is mounted in the stem of the lamp housing the resistance 1 and is heated thereby. Said container I has cemented to each end thereof a metal base 9. The lamp is thus self contained and is operable on current sources of commercial voltage without the need for external auxiliary apparatus.

When the considerable ultra-violet radiation from the discharge is desired for use external to 0 the lamp the container l is made of quartz or of When distinctly colored light is desired or when a higher luminous output or both is desired a luminescent material capable of emitting the desired radiation at the desired intensity is applied to the con- Luminescent glasses are also useful for Fluctuations in the light output of the lamp described above are reduced to a minimum when the voltage-current characteristic of the lamp is positive during the operation thereof. The lamp has a positive voltage-current characteristic when the tubular container I has an inside diameter of at least 30 mm., contains neon at a pressure of 2 mm. or less in addition to vaporizable mercury and has an operating discharge current The lamp described above is capable of operation on direct current or alternating current. 40 On direct current operation only one of the'electrodes need be provided with a heater element.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A lighting apparatus comprising in comblnation, an electric discharge lamp of the lowpressure, diffuse, positive column, luminous discharge type having spaced electrodes one of which is a thermionic electrode having a resistance-heater which is connected in series with the discharge between'said electrodes during operation of said device, the distance between said electrodes being such that at least per cent or the voltage of the current source on which saidlamp is designed to operate is dissipated in the lbw-pressure discharge between said electrodes during operation, and an iron wire-hydrogen filled resistor connected in series with said resistance heater to minimize the eflect of fluctuations in the supply voltage on the current density and the luminous output of the lowpressure'discharge in said lamp.

2. Alighting apparatus comprising in combination, an electric discharge lamp of the lowpressure, difluse, positive column, luminous discharge type having spaced electrodes one of which is a thermionic electrode having a resistance heater which is connected in series with the discharge between said electrodes during operation of said device, the distance between said electrodes being such that at least 60 per cent 01' the voltage of the current source on which said lamp is designed to operate is dissipated in the low pressure discharge between said electrodes during operation, and an iron wire-hydrogen filled resistor connected in series with said resistance heater to minimize the efiect of fluctuations in the supply voltage on the current density and the luminous output of the low-pressure discharge in said lamp, the resistance of said iron wire-hydrogen resistor being at most equal to that of said resistance heater.

3. A lighting apparatus comprising in combination, an electric discharge lamp of the lowpressure, diffuse, positive column luminous discharge type having therein mercury, neon at a pressure of about 2 millimeters and spaced electrodes one of which is a thermionicelectrode having a resistance heater which is connected in series with the discharge between said electrodes ARVED 1.0mm. MARTIN aaoaa. 

